Publikacje w roku 2008
Double notches: a zoom into the microphysics of coherent radio emission from pulsars
Dyks, J., Rudak, B., and Rankin, J. M.
2008 , 40 YEARS OF PULSARS: Millisecond Pulsars, Magnetars and More. AIP Conference Proceedings, Volume 983, pp. 148-150 (2008).
Abstract:
Three nearby objects: PSR B0950+08, B1929+10, and J0437-4715 are among the best studied and least understood radio pulsars. Their pulse profiles exhibit many peculiar properties, such as pedestal emission, double notches and lack of the radius-to-frequency mapping (RFM). We show that these properties can be understood in terms of the radio emission model that is based on inverse Compton scattering of longitudinal plasma waves. For a narrow spectrum of the plasma oscillations the model reproduces the observed narrowing of double notches with frequency. The emission mechanism is broad-band in the sense that different observed radio frequencies are due to differences in electrons' energy and not from different locations of emission regions. This explains the observed lack of RFM in J0437-4715 and the frequency-independent separation between the interpulse and main pulse in B0950+08 and B1929+10.
Discovery of VHE γ-rays from the high-frequency-peaked BL Lacertae object RGB J0152+017
Aharonian, F., Akhperjanian, A. G., Barres de Almeida, U., Bazer-Bachi, A. R., Behera, B., Beilicke, M., Benbow, W., Bernlöhr, K., Boisson, C., Borrel, V., Braun, I., Brion, E., Brucker, J., Bühler, R., Bulik, T., Büsching, I., Boutelier, T., Carrigan, S., Chadwick, P. M., Chaves, R. C. G., Chounet, L.-M., Clapson, A. C., Coignet, G., Cornils, R., Costamante, L., Dalton, M., Degrange, B., Dickinson, H. J., Djannati-Ataï, A., Domainko, W., O'C. Drury, L., Dubois, F., Dubus, G., Dyks, J., Egberts, K., Emmanoulopoulos, D., Espigat, P., Farnier, C., Feinstein, F., Fiasson, A., Förster, A., Fontaine, G., Füßling, M., Gabici, S., Gallant, Y. A., Giebels, B., Glicenstein, J.-F., Glück, B., Goret, P., Hadjichristidis, C., Hauser, D., Hauser, M., Heinzelmann, G., Henri, G., Hermann, G., Hinton, J. A., Hoffmann, A., Hofmann, W., Holleran, M., Hoppe, S., Horns, D., Jacholkowska, A., de Jager, O. C., Jung, I., Katarzyński, K., Kaufmann, S., Kendziorra, E., Kerschhaggl, M., Khangulyan, D., Khélifi, B., Keogh, D., Komin, N., Kosack, K., Lamanna, G., Latham, I. J., Lenain, J.-P., Lohse, T., Martin, J.-M., Martineau-Huynh, O., Marcowith, A., Masterson, C., Maurin, D., McComb, T. J. L., Moderski, R., Moulin, E., Naumann-Godo, M., de Naurois, M., Nedbal, D., Nekrassov, D., Nolan, S. J., Ohm, S., Olive, J.-P., de Oña Wilhelmi, E., Orford, K. J., Osborne, J. L., Ostrowski, M., Panter, M., Pedaletti, G., Pelletier, G., Petrucci, P.-O., Pita, S., Pühlhofer, G., Punch, M., Quirrenbach, A., Raubenheimer, B. C., Raue, M., Rayner, S. M., Renaud, M., Rieger, F., Ripken, J., Rob, L., Rosier-Lees, S., Rowell, G., Rudak, B., Ruppel, J., Sahakian, V., Santangelo, A., Schlickeiser, R., Schöck, F. M., Schröder, R., Schwanke, U., Schwarzburg, S., Schwemmer, S., Shalchi, A., Sol, H., Spangler, D., Stawarz, Ł., Steenkamp, R., Stegmann, C., Superina, G., Tam, P. H., Tavernet, J.-P., Terrier, R., van Eldik, C., Vasileiadis, G., Venter, C., Vialle, J.-P., Vincent, P., Vivier, M., Völk, H. J., Volpe, F., Wagner, S. J., Ward, M., Zdziarski, A. A., and Zech, A.
2008 , Astronomy and Astrophysics, Volume 481, Issue 3, 2008, pp.L103-L107
Abstract:

Aims. The BL Lac object RGB J0152+017 (z=0.080) was predicted to be a very high-energy (VHE; >100 GeV) γ-ray source, due to its high X-ray and radio fluxes. Our aim is to understand the radiative processes by investigating the observed emission and its production mechanism using the High Energy Stereoscopic System (HESS) experiment.

Methods. We report recent observations of the BL Lac source RGB J0152+017 made in late October and November 2007 with the HESS array consisting of four imaging atmospheric Cherenkov telescopes. Contemporaneous observations were made in X-rays by the Swift and RXTE satellites, in the optical band with the ATOM telescope, and in the radio band with the Nançay Radio Telescope.

Results. A signal of 173 γ-ray photons corresponding to a statistical significance of 6.6σ was found in the data. The energy spectrum of the source can be described by a powerlaw with a spectral index of Γ=2.95±0.36stat± 0.20syst. The integral flux above 300 GeV corresponds to ~2% of the flux of the Crab nebula. The source spectral energy distribution (SED) can be described using a two-component non-thermal synchrotron self-Compton (SSC) leptonic model, except in the optical band, which is dominated by a thermal host galaxy component. The parameters that are found are very close to those found in similar SSC studies in TeV blazars.

Conclusions. RGB J0152+017 is discovered as a source of VHE γ-rays by HESS The location of its synchrotron peak, as derived from the SED in Swift data, allows clear classification as a high-frequency-peaked BL Lac (HBL).
Discovery of very-high-energy γ-ray emission from the vicinity of PSR J1913+1011 with HESS
Aharonian, F., Akhperjanian, A. G., Barres de Almeida, U., Bazer-Bachi, A. R., Behera, B., Beilicke, M., Benbow, W., Bernlöhr, K., Boisson, C., Bolz, O., Borrel, V., Braun, I., Brion, E., Brown, A. M., Bühler, R., Bulik, T., Büsching, I., Boutelier, T., Carrigan, S., Chadwick, P. M., Chounet, L.-M., Clapson, A. C., Coignet, G., Cornils, R., Costamante, L., Dalton, M., Degrange, B., Dickinson, H. J., Djannati-Ataï, A., Domainko, W., O'C. Drury, L., Dubois, F., Dubus, G., Dyks, J., Egberts, K., Emmanoulopoulos, D., Espigat, P., Farnier, C., Feinstein, F., Fiasson, A., Förster, A., Fontaine, G., Funk, S., Füßling, M., Gallant, Y. A., Giebels, B., Glicenstein, J. F., Glück, B., Goret, P., Hadjichristidis, C., Hauser, D., Hauser, M., Heinzelmann, G., Henri, G., Hermann, G., Hinton, J. A., Hoffmann, A., Hofmann, W., Holleran, M., Hoppe, S., Horns, D., Jacholkowska, A., de Jager, O. C., Jung, I., Katarzyński, K., Kendziorra, E., Kerschhaggl, M., Khélifi, B., Keogh, D., Komin, N., Kosack, K., Lamanna, G., Latham, I. J., Lemière, A., Lemoine-Goumard, M., Lenain, J.-P., Lohse, T., Martin, J. M., Martineau-Huynh, O., Marcowith, A., Masterson, C., Maurin, D., Maurin, G., McComb, T. J. L., Moderski, R., Moulin, E., de Naurois, M., Nedbal, D., Nolan, S. J., Ohm, S., Olive, J.-P., de Oña Wilhelmi, E., Orford, K. J., Osborne, J. L., Ostrowski, M., Panter, M., Pedaletti, G., Pelletier, G., Petrucci, P.-O., Pita, S., Pühlhofer, G., Punch, M., Raubenheimer, B. C., Raue, M., Rayner, S. M., Reimer, O., Renaud, M., Ripken, J., Rob, L., Rolland, L., Rosier-Lees, S., Rowell, G., Rudak, B., Ruppel, J., Sahakian, V., Santangelo, A., Schlickeiser, R., Schöck, F., Schröder, R., Schwanke, U., Schwarzburg, S., Schwemmer, S., Shalchi, A., Sol, H., Spangler, D., Stawarz, Ł., Steenkamp, R., Stegmann, C., Superina, G., Tam, P. H., Tavernet, J.-P., Terrier, R., van Eldik, C., Vasileiadis, G., Venter, C., Vialle, J. P., Vincent, P., Vivier, M., Völk, H. J., Volpe, F., Wagner, S. J., Ward, M., Zdziarski, A. A., and Zech, A.
2008 , Astronomy and Astrophysics, Volume 484, Issue 2, 2008, pp.435-440
Abstract:
The HESS experiment, an array of four Imaging Atmospheric Cherenkov Telescopes with high sensitivity and large field-of-view, has been used to search for emitters of very-high-energy (VHE, >100 GeV) γ-rays along the Galactic plane, covering the region 30° < l < 60°, 280° < l < 330°, and -3° < b < 3°. In this continuation of the HESS Galactic Plane Scan, a new extended VHE γ-ray source was discovered at α2000=19^h12^m49^s, δ2000=+10°09´06´´(HESS J1912+101). Its integral flux between 1-10 TeV is ~10% of the Crab Nebula flux in the same energy range. The measured energy spectrum can be described by a power law dN/dE ˜ E with a photon index Γ = 2.7 ± 0.2stat± 0.3sys. HESS J1912+101 is plausibly associated with the high spin-down luminosity pulsar PSR J1913+1011. We also discuss associations with an as yet unconfirmed SNR candidate proposed from low frequency radio observation and/or with molecular clouds found in 13CO data.
Dust Size Effect On IR Colors Of AGB Stars
Wang, H., Jiang, B. W., and Szczerba, R.
2008 , The Art of Modeling Stars in the 21st Century, Proceedings of the International Astronomical Union, IAU Symposium, Volume 252, p. 263-264
Abstract:
With the Mie theory and the radiative transfer model, we studied the effect of dust size on the infrared color indexes concerning special filters used in the space infrared missions and typical filters in the near-infrared, of AGB stars with typical oxygen-rich and carbon-rich dust shells. It is found the most affected bands are the near-infrared bands JHK and the Spitzer IRAC bands, meanwhile the wavebands with reference wavelength longer than 10 μm is little affected. The effect increases fast with the mass loss rate. We also discussed the potential to distinguish the O-rich and C-rich dusts, and the difference in IR colors between the AGB stars and other IR sources like YSOs and galaxies.
Energy Spectrum of Cosmic-Ray Electrons at TeV Energies
Aharonian, F., Akhperjanian, A. G., Barres de Almeida, U., Bazer-Bachi, A. R., Becherini, Y., Behera, B., Benbow, W., Bernlöhr, K., Boisson, C., Bochow, A., Borrel, V., Braun, I., Brion, E., Brucker, J., Brun, P., Bühler, R., Bulik, T., Büsching, I., Boutelier, T., Carrigan, S., Chadwick, P. M., Charbonnier, A., Chaves, R. C. G., Cheesebrough, A., Chounet, L.-M., Clapson, A. C., Coignet, G., Costamante, L., Dalton, M., Degrange, B., Deil, C., Dickinson, H. J., Djannati-Ataï, A., Domainko, W., Drury, L. O. '., Dubois, F., Dubus, G., Dyks, J., Dyrda, M., Egberts, K., Emmanoulopoulos, D., Espigat, P., Farnier, C., Feinstein, F., Fiasson, A., Förster, A., Fontaine, G., Füßling, M., Gabici, S., Gallant, Y. A., Gérard, L., Giebels, B., Glicenstein, J. F., Glück, B., Goret, P., Hadjichristidis, C., Hauser, D., Hauser, M., Heinz, S., Heinzelmann, G., Henri, G., Hermann, G., Hinton, J. A., Hoffmann, A., Hofmann, W., Holleran, M., Hoppe, S., Horns, D., Jacholkowska, A., de Jager, O. C., Jung, I., Katarzyński, K., Kaufmann, S., Kendziorra, E., Kerschhaggl, M., Khangulyan, D., Khélifi, B., Keogh, D., Komin, N., Kosack, K., Lamanna, G., Lenain, J.-P., Lohse, T., Marandon, V., Martin, J. M., Martineau-Huynh, O., Marcowith, A., Maurin, D., McComb, T. J. L., Medina, C., Moderski, R., Moulin, E., Naumann-Godo, M., de Naurois, M., Nedbal, D., Nekrassov, D., Niemiec, J., Nolan, S. J., Ohm, S., Olive, J.-F., de Oña Wilhelmi, E., Orford, K. J., Osborne, J. L., Ostrowski, M., Panter, M., Pedaletti, G., Pelletier, G., Petrucci, P.-O., Pita, S., Pühlhofer, G., Punch, M., Quirrenbach, A., Raubenheimer, B. C., Raue, M., Rayner, S. M., Renaud, M., Rieger, F., Ripken, J., Rob, L., Rosier-Lees, S., Rowell, G., Rudak, B., Rulten, C. B., Ruppel, J., Sahakian, V., Santangelo, A., Schlickeiser, R., Schöck, F. M., Schröder, R., Schwanke, U., Schwarzburg, S., Schwemmer, S., Shalchi, A., Skilton, J. L., Sol, H., Spangler, D., Stawarz, Ł., Steenkamp, R., Stegmann, C., Superina, G., Tam, P. H., Tavernet, J.-P., Terrier, R., Tibolla, O., van Eldik, C., Vasileiadis, G., Venter, C., Vialle, J. P., Vincent, P., Vivier, M., Völk, H. J., Volpe, F., Wagner, S. J., Ward, M., Zdziarski, A. A., and Zech, A.
2008 , Physical Review Letters, vol. 101, Issue 26, id. 261104
Abstract:
The very large collection area of ground-based γ-ray telescopes gives them a substantial advantage over balloon or satellite based instruments in the detection of very-high-energy (>600GeV) cosmic-ray electrons. Here we present the electron spectrum derived from data taken with the High Energy Stereoscopic System (H.E.S.S.) of imaging atmospheric Cherenkov telescopes. In this measurement, the first of this type, we are able to extend the measurement of the electron spectrum beyond the range accessible to direct measurements. We find evidence for a substantial steepening in the energy spectrum above 600 GeV compared to lower energies.
Discovery of very high energy gamma-ray emission coincident with molecular clouds in the W 28 (G6.4-0.1) field
Aharonian, F., Akhperjanian, A. G., Bazer-Bachi, A. R., Behera, B., Beilicke, M., Benbow, W., Berge, D., Bernlöhr, K., Boisson, C., Bolz, O., Borrel, V., Braun, I., Brion, E., Brown, A. M., Bühler, R., Bulik, T., Büsching, I., Boutelier, T., Carrigan, S., Chadwick, P. M., Chounet, L.-M., Clapson, A. C., Coignet, G., Cornils, R., Costamante, L., Degrange, B., Dickinson, H. J., Djannati-Ataï, A., Domainko, W., O'C. Drury, L., Dubus, G., Dyks, J., Egberts, K., Emmanoulopoulos, D., Espigat, P., Farnier, C., Feinstein, F., Fiasson, A., Förster, A., Fontaine, G., Fukui, Y., Funk, S., Funk, S., Füßling, M., Gallant, Y. A., Giebels, B., Glicenstein, J. F., Glück, B., Goret, P., Hadjichristidis, C., Hauser, D., Hauser, M., Heinzelmann, G., Henri, G., Hermann, G., Hinton, J. A., Hoffmann, A., Hofmann, W., Holleran, M., Hoppe, S., Horns, D., Jacholkowska, A., de Jager, O. C., Kendziorra, E., Kerschhaggl, M., Khélifi, B., Komin, N., Kosack, K., Lamanna, G., Latham, I. J., Le Gallou, R., Lemière, A., Lemoine-Goumard, M., Lenain, J.-P., Lohse, T., Martin, J. M., Martineau-Huynh, O., Marcowith, A., Masterson, C., Maurin, G., McComb, T. J. L., Moderski, R., Moriguchi, Y., Moulin, E., de Naurois, M., Nedbal, D., Nolan, S. J., Olive, J.-P., Orford, K. J., Osborne, J. L., Ostrowski, M., Panter, M., Pedaletti, G., Pelletier, G., Petrucci, P.-O., Pita, S., Pühlhofer, G., Punch, M., Ranchon, S., Raubenheimer, B. C., Raue, M., Rayner, S. M., Reimer, O., Renaud, M., Ripken, J., Rob, L., Rolland, L., Rosier-Lees, S., Rowell, G., Rudak, B., Ruppel, J., Sahakian, V., Santangelo, A., Saugé, L., Schlenker, S., Schlickeiser, R., Schröder, R., Schwanke, U., Schwarzburg, S., Schwemmer, S., Shalchi, A., Sol, H., Spangler, D., Stawarz, Ł., Steenkamp, R., Stegmann, C., Superina, G., Takeuchi, T., Tam, P. H., Tavernet, J.-P., Terrier, R., van Eldik, C., Vasileiadis, G., Venter, C., Vialle, J. P., Vincent, P., Vivier, M., Völk, H. J., Volpe, F., Wagner, S. J., and Ward, M.
2008 , Astronomy and Astrophysics, Volume 481, Issue 2, 2008, pp.401-410
Abstract:

Aims. Observations of shell-type supernova remnants (SNRs) in the GeV to multi-TeV γ-ray band, coupled with those at millimetre radio wavelengths, are motivated by the search for cosmic-ray accelerators in our Galaxy. The old-age mixed-morphology SNR W 28 (distance ~2 kpc) is a prime target due to its interaction with molecular clouds along its northeastern boundary and other clouds situated nearby.

Methods. We observed the W 28 field (for ~40 h) at very high energy (VHE) γ-ray energies (E > 0.1 TeV) with the HESS. Cherenkov telescopes. A reanalysis of EGRET E > 100 MeV data was also undertaken. Results from the NANTEN 4 m telescope Galactic plane survey and other CO observations were used to study molecular clouds.

Results. We have discovered VHE γ-ray emission (HESS J1801-233) coincident with the northeastern boundary of W 28 and a complex of sources (HESS J1800-240A, B and C) ~0.5° south of W 28 in the Galactic disc. The EGRET source (GRO J1801-2320) is centred on HESS J1801-233 but may also be related to HESS J1800-240 given the large EGRET point spread function. The VHE differential photon spectra are well fit by pure power laws with indices Γ ~2.3 to 2.7. The spectral indices of HESS J1800-240A, B, and C are consistent within statistical errors. All VHE sources are ~10' in intrinsic radius except for HESS J1800-240C, which appears pointlike. The NANTEN 12CO(J = 1-0) data reveal molecular clouds positionally associating with the VHE emission, spanning a ~15 km s-1 range in local standard of rest velocity.

Conclusions. The VHE/molecular cloud association could indicate a hadronic origin for HESS J1801-233 and HESS J1800-240, and several cloud components in projection may contribute to the VHE emission. The clouds have components covering a broad velocity range encompassing the distance estimates for W 28 (~2 kpc) and extending up to ~4 kpc. Assuming hadronic origin and distances of 2 and 4 kpc for cloud components, the required cosmic-ray density enhancement factors (with respect to the solar value) are in the range ~10 to ~30. If situated at 2 kpc distance, such cosmic-ray densities may be supplied by SNRs like W 28. Additionally and/or alternatively, particle acceleration may come from several catalogued SNRs and SNR candidates, the energetic ultra compact HII region W 28A2, and the HII regions M 8 and M 20, along with their associated open clusters. Further sub-mm observations would be recommended to probe in detail the dynamics of the molecular clouds at velocites > 10 km s-1 and their possible connection to W 28.
Energy spectra are only available in electronic form at http://www.aanda.org
Discovery of a VHE gamma-ray source coincident with the supernova remnant CTB 37A
Aharonian, F., Akhperjanian, A. G., Barres de Almeida, U., Bazer-Bachi, A. R., Behera, B., Beilicke, M., Benbow, W., Bernlöhr, K., Boisson, C., Borrel, V., Braun, I., Brion, E., Brucker, J., Bühler, R., Bulik, T., Büsching, I., Boutelier, T., Carrigan, S., Chadwick, P. M., Chaves, R., Chounet, L.-M., Clapson, A. C., Coignet, G., Cornils, R., Costamante, L., Dalton, M., Degrange, B., Dickinson, H. J., Djannati-Ataï, A., Domainko, W., O'C. Drury, L., Dubois, F., Dubus, G., Dyks, J., Egberts, K., Emmanoulopoulos, D., Espigat, P., Farnier, C., Feinstein, F., Fiasson, A., Förster, A., Fontaine, G., Funk, S., Füßling, M., Gabici, S., Gallant, Y. A., Giebels, B., Glicenstein, J. F., Glück, B., Goret, P., Hadjichristidis, C., Hauser, D., Hauser, M., Heinzelmann, G., Henri, G., Hermann, G., Hinton, J. A., Hoffmann, A., Hofmann, W., Holleran, M., Hoppe, S., Horns, D., Jacholkowska, A., de Jager, O. C., Jung, I., Katarzyński, K., Kaufmann, S., Kendziorra, E., Kerschhaggl, M., Khangulyan, D., Khélifi, B., Keogh, D., Komin, N., Kosack, K., Lamanna, G., Latham, I. J., Lemoine-Goumard, M., Lenain, J.-P., Lohse, T., Martin, J. M., Martineau-Huynh, O., Marcowith, A., Masterson, C., Maurin, D., McComb, T. J. L., Moderski, R., Moulin, E., Nakajima, H., Naumann-Godo, M., de Naurois, M., Nedbal, D., Nekrassov, D., Nolan, S. J., Ohm, S., Olive, J.-P., de Oña Wilhelmi, E., Orford, K. J., Osborne, J. L., Ostrowski, M., Panter, M., Pedaletti, G., Pelletier, G., Petrucci, P.-O., Pita, S., Pühlhofer, G., Punch, M., Quirrenbach, A., Raubenheimer, B. C., Raue, M., Rayner, S. M., Reimer, O., Renaud, M., Rieger, F., Ripken, J., Rob, L., Rosier-Lees, S., Rowell, G., Rudak, B., Ruppel, J., Sahakian, V., Santangelo, A., Schlickeiser, R., Schöck, F. M., Schröder, R., Schwanke, U., Schwarzburg, S., Schwemmer, S., Shalchi, A., Skilton, J. L., Sol, H., Spangler, D., Stawarz, Ł., Steenkamp, R., Stegmann, C., Superina, G., Tam, P. H., Tavernet, J.-P., Terrier, R., Tibolla, O., van Eldik, C., Vasileiadis, G., Venter, C., Vialle, J. P., Vincent, P., Vivier, M., Völk, H. J., Volpe, F., Wagner, S. J., Ward, M., Zdziarski, A. A., and Zech, A.
2008 , Astronomy and Astrophysics, Volume 490, Issue 2, 2008, pp.685-693
Abstract:

Aims. The supernova remnant (SNR) complex CTB 37 is an interesting candidate for observations with very high energy (VHE) γ-ray telescopes such as HESS. In this region, three SNRs are seen. One of them is potentially associated with several molecular clouds, a circumstance that can be used to probe the acceleration of hadronic cosmic rays.

Methods. This region was observed with the HESS Cherenkov telescopes and the data were analyzed with standard HESS procedures. Recent X-ray observations with Chandra and XMM-Newton were used to search for X-ray counterparts.

Results. The discovery of a new VHE γ-ray source HESS J1714-385 coincident with the remnant CTB 37A is reported. The energy spectrum is well described by a power-law with a photon index of Γ = 2.30 ± 0.13 and a differential flux at 1 TeV of Φ0 = (8.7 ± 1.0stat ± 1.8sys) × 10-13 cm-2 s-1 TeV-1. The integrated flux above 1 TeV is equivalent to 3% of the flux of the Crab nebula above the same energy. This VHE γ-ray source is a counterpart candidate for the unidentified EGRET source 3EG J1714-3857. The observed VHE emission is consistent with the molecular gas distribution around CTB 37A; a close match is expected in a hadronic scenario for γ-ray production. The X-ray observations reveal the presence of thermal X-rays from the NE part of the SNR. In the NW part of the remnant, an extended non-thermal X-ray source, CXOU J171419.8-383023, is discovered as well. Possible connections of the X-ray emission to the newly found VHE source are discussed.
Carriers of the mid-IR emission bands in PNe reanalysed. Evidence of a link between circumstellar and interstellar aromatic dust
Joblin, C., Szczerba, R., Berné, O., and Szyszka, C.
2008 , Astronomy and Astrophysics, Volume 490, Issue 1, 2008, pp.189-196
Abstract:

Context. It has been shown that the diversity of the aromatic emission features can be rationalized into different classes of objects, in which differences between circumstellar and interstellar matter are emphasised.

Aims. We probe the links between the mid-IR emitters observed in planetary nebulae (PNe) and their counterparts in the interstellar medium in order to probe a scenario in which the latter have been formed in the circumstellar environment of evolved stars.

Methods. The mid-IR (6-14 μm) emission spectra of PNe and compact H II regions were analysed on the basis of previous work on photodissociation regions (PDRs). Galactic, Large Magellanic Cloud (LMC), and Small Magellanic Cloud (SMC) objects were considered in our sample.

Results. We show that the mid-IR emission of PNe can be decomposed as the sum of six components. Some components made of polycyclic aromatic hydrocarbon (PAH) and very small grain (VSG) populations are similar to those observed in PDRs. Others are fitted in an evolutionary scenario involving the destruction of the aliphatic component observed in the post-AGB stage, as well as strong processing of PAHs in the extreme conditions of PNe that leads to a population of very large ionized PAHs. This species called PAHx are proposed as the carriers of a characteristic band at 7.90 μm. This band can be used as part of diagnostics that identify PNe in nearby galaxies and is also observed in galactic compact H II regions.

Conclusions. These results support the formation of the aromatic very small dust particles in the envelopes of evolved stars, in the Milky Way, as well as in the LMC and SMC, and their subsequent survival in the interstellar medium.
This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA.
Tables A.1 and A.2 are only available in electronic form at http://www.aanda.org
Chandra and HESS observations of the supernova remnant CTB 37B
Aharonian, F., Akhperjanian, A. G., Barres de Almeida, U., Bazer-Bachi, A. R., Behera, B., Beilicke, M., Benbow, W., Bernlöhr, K., Boisson, C., Borrel, V., Braun, I., Brion, E., Brucker, J., Bühler, R., Bulik, T., Büsching, I., Boutelier, T., Carrigan, S., Chadwick, P. M., Chaves, R. C. G., Chounet, L.-M., Clapson, A. C., Coignet, G., Cornils, R., Costamante, L., Dalton, M., Degrange, B., Dickinson, H. J., Djannati-Ataï, A., Domainko, W., O'C. Drury, L., Dubois, F., Dubus, G., Dyks, J., Egberts, K., Emmanoulopoulos, D., Espigat, P., Farnier, C., Feinstein, F., Fiasson, A., Förster, A., Fontaine, G., Funk, S., Füßling, M., Gabici, S., Gallant, Y. A., Giebels, B., Glicenstein, J. F., Glück, B., Goret, P., Hadjichristidis, C., Hauser, D., Hauser, M., Heinzelmann, G., Henri, G., Hermann, G., Hinton, J. A., Hoffmann, A., Hofmann, W., Holleran, M., Hoppe, S., Horns, D., Jacholkowska, A., de Jager, O. C., Jung, I., Katarzyński, K., Kaufmann, S., Kendziorra, E., Kerschhaggl, M., Khangulyan, D., Khélifi, B., Keogh, D., Komin, N., Kosack, K., Lamanna, G., Latham, I. J., Lemoine-Goumard, M., Lenain, J.-P., Lohse, T., Martin, J. M., Martineau-Huynh, O., Marcowith, A., Masterson, C., Maurin, D., McComb, T. J. L., Moderski, R., Moulin, E., Naumann-Godo, M., de Naurois, M., Nedbal, D., Nekrassov, D., Nolan, S. J., Ohm, S., Olive, J.-P., de Oña Wilhelmi, E., Orford, K. J., Osborne, J. L., Ostrowski, M., Panter, M., Pedaletti, G., Pelletier, G., Petrucci, P.-O., Pita, S., Pühlhofer, G., Punch, M., Quirrenbach, A., Raubenheimer, B. C., Raue, M., Rayner, S. M., Renaud, M., Rieger, F., Reimer, O., Ripken, J., Rob, L., Rosier-Lees, S., Rowell, G., Rudak, B., Ruppel, J., Sahakian, V., Santangelo, A., Schlickeiser, R., Schöck, F. M., Schröder, R., Schwanke, U., Schwarzburg, S., Schwemmer, S., Shalchi, A., Skilton, J. L., Sol, H., Spangler, D., Stawarz, Ł., Steenkamp, R., Stegmann, C., Superina, G., Tam, P. H., Tavernet, J.-P., Terrier, R., van Eldik, C., Vasileiadis, G., Venter, C., Vialle, J. P., Vincent, P., Vivier, M., Völk, H. J., Volpe, F., Wagner, S. J., Ward, M., Zdziarski, A. A., and Zech, A.
2008 , Astronomy and Astrophysics, Volume 486, Issue 3, 2008, pp.829-836
Abstract:
We discovered the >100 GeV γ-ray source, HESS J1713-381, apparently associated with the shell-type supernova remnant (SNR) CTB 37B, using HESS in 2006. In 2007 we performed X-ray follow-up observations with Chandra with the aim of identifying a synchrotron counterpart to the TeV source and/or thermal emission from the SNR shell. These new Chandra data, together with additional TeV data, allow us to investigate the nature of this object in much greater detail than was previously possible. The new X-ray data reveal thermal emission from a ~4' region in close proximity to the radio shell of CTB 37B. The temperature of this emission implies an age for the remnant of ~5000 years and an ambient gas density of ~0.5 cm-3. Both these estimates are considerably uncertain due to the asymmetry of the SNR and possible modifications of the kinematics due to efficient cosmic ray (CR) acceleration. A bright (≈ 7 × 10-13 erg cm-2 s-1) and unresolved (<1 arcsec) source (CXOU J171405.7-381031), with a soft (Γ≈3.3) non-thermal spectrum is also detected in coincidence with the radio shell. Absorption indicates a column density consistent with the thermal emission from the shell, suggesting a genuine association rather than a chance alignment. The observed TeV morphology is consistent with an origin in the complete shell of CTB 37B. The lack of diffuse non-thermal X-ray emission suggests an origin of the γ-ray emission via the decay of neutral pions produced in interactions of protons and nuclei, rather than inverse Compton (IC) emission from relativistic electrons.
A dynamical analysis of the 14 Herculis planetary system
Goździewski, K., Migaszewski, C., and Konacki, M.
2008 , Monthly Notices of the Royal Astronomical Society, Volume 385, Issue 2, pp. 957-966.
Abstract:
Precision radial velocity measurements of the Sun-like dwarf 14 Herculis published by Naef et al., Butler et al. and Wittenmyer, Endl & Cochran reveal a Jovian planet in a 1760-d orbit and a trend indicating the second distant object. On the grounds of dynamical considerations, we test a hypothesis that the trend can be explained by the presence of an additional giant planet. We derive dynamical limits to the orbital parameters of the putative outer Jovian companion in an orbit within ~13 au. In this case, the mutual interactions between the Jovian planets are important for the long-term stability of the system. The best self-consistent and stable Newtonian fit to an edge-on configuration of Jovian planets has the outer planet in 9-au orbit with a moderate eccentricity of ~0.2 and confined to a zone spanned by the low-order mean motion resonances 5:1 and 6:1. This solution lies in a shallow minimum of (χ2ν)1/2 and persists over a wide range of the system inclination. Other stable configurations within 1σ confidence interval of the best fit are possible for the semimajor axis of the outer planet in the range of (6,13) au and the eccentricity in the range of (0, 0.3). The orbital inclination cannot yet be determined but when it decreases, both planetary masses approach ~10mJ and for i ~ 30° the hierarchy of the masses is reversed.
Exploring a SNR/molecular cloud association within HESS J1745-303
Aharonian, F., Akhperjanian, A. G., Barres de Almeida, U., Bazer-Bachi, A. R., Behera, B., Beilicke, M., Benbow, W., Bernlöhr, K., Boisson, C., Bolz, O., Borrel, V., Braun, I., Brion, E., Brown, A. M., Bühler, R., Bulik, T., Büsching, I., Boutelier, T., Carrigan, S., Chadwick, P. M., Chounet, L.-M., Clapson, A. C., Coignet, G., Cornils, R., Costamante, L., Dalton, M., Degrange, B., Dickinson, H. J., Djannati-Ataï, A., Domainko, W., O'C. Drury, L., Dubois, F., Dubus, G., Dyks, J., Egberts, K., Emmanoulopoulos, D., Espigat, P., Farnier, C., Feinstein, F., Fiasson, A., Förster, A., Fontaine, G., Funk, S., Füßling, M., Gallant, Y. A., Giebels, B., Glicenstein, J. F., Glück, B., Goret, P., Hadjichristidis, C., Hauser, D., Hauser, M., Heinzelmann, G., Henri, G., Hermann, G., Hinton, J. A., Hoffmann, A., Hofmann, W., Holleran, M., Hoppe, S., Horns, D., Jacholkowska, A., de Jager, O. C., Jung, I., Katarzyński, K., Kendziorra, E., Kerschhaggl, M., Khélifi, B., Keogh, D., Komin, N., Kosack, K., Lamanna, G., Latham, I. J., Lemoine-Goumard, M., Lenain, J.-P., Lohse, T., Martin, J. M., Martineau-Huynh, O., Marcowith, A., Masterson, C., Maurin, D., McComb, T. J. L., Moderski, R., Moulin, E., Naumann-Godo, M., de Naurois, M., Nedbal, D., Nekrassov, D., Nolan, S. J., Ohm, S., Olive, J.-P., de Oña Wilhelmi, E., Orford, K. J., Osborne, J. L., Ostrowski, M., Panter, M., Pedaletti, G., Pelletier, G., Petrucci, P.-O., Pita, S., Pühlhofer, G., Punch, M., Raubenheimer, B. C., Raue, M., Rayner, S. M., Renaud, M., Ripken, J., Rob, L., Rosier-Lees, S., Rowell, G., Rudak, B., Ruppel, J., Sahakian, V., Santangelo, A., Schlickeiser, R., Schöck, F. M., Schröder, R., Schwanke, U., Schwarzburg, S., Schwemmer, S., Shalchi, A., Sol, H., Spangler, D., Stawarz, Ł., Steenkamp, R., Stegmann, C., Superina, G., Tam, P. H., Tavernet, J.-P., Terrier, R., van Eldik, C., Vasileiadis, G., Venter, C., Vialle, J. P., Vincent, P., Vivier, M., Völk, H. J., Volpe, F., Wagner, S. J., Ward, M., Zdziarski, A. A., and Zech, A.
2008 , Astronomy and Astrophysics, Volume 483, Issue 2, 2008, pp.509-517
Abstract:

Aims. HESS J1745-303 is an extended, unidentified VHE (very high energy) gamma-ray source discovered using HESS in the Galactic Plane Survey. Since no obvious counterpart has previously been found in longer-wavelength data, the processes that power the VHE emission are not well understood.

Methods. Combining the latest VHE data with recent XMM-Newton observations and a variety of source catalogs and lower-energy survey data, we attempt to match (from an energetic and positional standpoint) the various parts of the emission of HESS J1745-303 with possible candidates.

Results. Though no single counterpart is found to fully explain the VHE emission, we postulate that at least a fraction of the VHE source may be explained by a supernova-remnant/molecular-cloud association and/or a high-spin-down-flux pulsar.
HESS observations and VLT spectroscopy of PG 1553+113
Aharonian, F., Akhperjanian, A. G., Barres de Almeida, U., Bazer-Bachi, A. R., Behera, B., Beilicke, M., Benbow, W., Bernlöhr, K., Boisson, C., Bolz, O., Borrel, V., Braun, I., Brion, E., Brown, A. M., Bühler, R., Bulik, T., Büsching, I., Boutelier, T., Carrigan, S., Chadwick, P. M., Chounet, L.-M., Clapson, A. C., Coignet, G., Cornils, R., Costamante, L., Dalton, M., Degrange, B., Dickinson, H. J., Djannati-Ataï, A., Domainko, W., O'C. Drury, L., Dubois, F., Dubus, G., Dyks, J., Egberts, K., Emmanoulopoulos, D., Espigat, P., Farnier, C., Feinstein, F., Fiasson, A., Förster, A., Fontaine, G., Funk, S., Füßling, M., Gallant, Y. A., Giebels, B., Glicenstein, J. F., Glück, B., Goret, P., Hadjichristidis, C., Hauser, D., Hauser, M., Heinzelmann, G., Henri, G., Hermann, G., Hinton, J. A., Hoffmann, A., Hofmann, W., Holleran, M., Hoppe, S., Horns, D., Jacholkowska, A., de Jager, O. C., Jung, I., Katarzyński, K., Kendziorra, E., Kerschhaggl, M., Khélifi, B., Keogh, D., Komin, N., Kosack, K., Lamanna, G., Latham, I. J., Lemière, A., Lemoine-Goumard, M., Lenain, J.-P., Lohse, T., Martin, J. M., Martineau-Huynh, O., Marcowith, A., Masterson, C., Maurin, D., Maurin, G., McComb, T. J. L., Moderski, R., Moulin, E., de Naurois, M., Nedbal, D., Nolan, S. J., Ohm, S., Olive, J.-P., de Oña Wilhelmi, E., Orford, K. J., Osborne, J. L., Ostrowski, M., Panter, M., Pedaletti, G., Pelletier, G., Petrucci, P.-O., Pita, S., Pühlhofer, G., Punch, M., Ranchon, S., Raubenheimer, B. C., Raue, M., Rayner, S. M., Renaud, M., Ripken, J., Rob, L., Rolland, L., Rosier-Lees, S., Rowell, G., Rudak, B., Ruppel, J., Sahakian, V., Santangelo, A., Schlickeiser, R., Schöck, F., Schröder, R., Schwanke, U., Schwarzburg, S., Schwemmer, S., Shalchi, A., Sol, H., Spangler, D., Stawarz, Ł., Steenkamp, R., Stegmann, C., Superina, G., Tam, P. H., Tavernet, J.-P., Terrier, R., van Eldik, C., Vasileiadis, G., Venter, C., Vialle, J. P., Vincent, P., Vivier, M., Völk, H. J., Volpe, F., Wagner, S. J., Ward, M., Zdziarski, A. A., and Zech, A.
2008 , Astronomy and Astrophysics, Volume 477, Issue 2, 2008, pp.481-489
Abstract:
Aims:The properties of the very high energy (VHE; E > 100 GeV) γ-ray emission from the high-frequency peaked BL Lac PG 1553+113 are investigated. An attempt is made to measure the currently unknown redshift of this object.

Methods. VHE Observations of PG 1553+113 were made with the High Energy Stereoscopic System (HESS) in 2005 and 2006. H + K (1.45-2.45 μm) spectroscopy of PG 1553+113 was performed in March 2006 with SINFONI, an integral field spectrometer of the ESO Very Large Telescope (VLT) in Chile.

Results. A VHE signal, ~10 standard deviations, is detected by HESS during the 2 years of observations (24.8 h live time). The integral flux above 300 GeV is (4.6 ± 0.6_stat ± 0.9_syst) × 10-12 cm-2 s-1, corresponding to ~3.4% of the flux from the Crab Nebula above the same threshold. The time-averaged energy spectrum is measured from 225 GeV to ~1.3 TeV, and is characterized by a very soft power law (photon index of Γ = 4.5 ± 0.3_stat ± 0.1_syst). No evidence for any flux or spectral variations is found on any sampled time scale within the VHE data. The redshift of PG 1553+113 could not be determined. Indeed, even though the measured SINFONI spectrum is the most sensitive ever reported for this object at near infrared wavelengths, and the sensitivity is comparable to the best spectroscopy at other wavelengths, no absorption or emission lines were found in the H+K spectrum presented here.
HESS upper limits for Kepler's supernova remnant
Aharonian, F., Akhperjanian, A. G., Barres de Almeida, U., Bazer-Bachi, A. R., Behera, B., Beilicke, M., Benbow, W., Berge, D., Bernlöhr, K., Boisson, C., Bolz, O., Borrel, V., Braun, I., Brion, E., Brucker, J., Bühler, R., Bulik, T., Büsching, I., Boutelier, T., Carrigan, S., Chadwick, P. M., Chounet, L.-M., Clapson, A. C., Coignet, G., Cornils, R., Costamante, L., Dalton, M., Degrange, B., Dickinson, H. J., Djannati-Ataï, A., Domainko, W., O'C. Drury, L., Dubois, F., Dubus, G., Dyks, J., Egberts, K., Emmanoulopoulos, D., Espigat, P., Farnier, C., Feinstein, F., Fiasson, A., Förster, A., Fontaine, G., Füßling, M., Gallant, Y. A., Giebels, B., Glicenstein, J. F., Glück, B., Goret, P., Hadjichristidis, C., Hauser, D., Hauser, M., Heinzelmann, G., Henri, G., Hermann, G., Hinton, J. A., Hoffmann, A., Hofmann, W., Holleran, M., Hoppe, S., Horns, D., Jacholkowska, A., de Jager, O. C., Jung, I., Katarzyński, K., Kendziorra, E., Kerschhaggl, M., Khélifi, B., Keogh, D., Komin, N., Kosack, K., Lamanna, G., Latham, I. J., Lemoine-Goumard, M., Lenain, J.-P., Lohse, T., Martin, J. M., Martineau-Huynh, O., Marcowith, A., Masterson, C., Maurin, D., McComb, T. J. L., Moderski, R., Moulin, E., Naumann-Godo, M., de Naurois, M., Nedbal, D., Nekrassov, D., Nolan, S. J., Ohm, S., Olive, J.-P., de Oña Wilhelmi, E., Orford, K. J., Osborne, J. L., Ostrowski, M., Panter, M., Pedaletti, G., Pelletier, G., Petrucci, P.-O., Pita, S., Pühlhofer, G., Punch, M., Quirrenbach, A., Raubenheimer, B. C., Raue, M., Rayner, S. M., Renaud, M., Ripken, J., Rob, L., Rosier-Lees, S., Rowell, G., Rudak, B., Ruppel, J., Sahakian, V., Santangelo, A., Schlickeiser, R., Schöck, F. M., Schröder, R., Schwanke, U., Schwarzburg, S., Schwemmer, S., Shalchi, A., Sol, H., Spangler, D., Stawarz, Ł., Steenkamp, R., Stegmann, C., Superina, G., Tam, P. H., Tavernet, J.-P., Terrier, R., van Eldik, C., Vasileiadis, G., Venter, C., Vialle, J. P., Vincent, P., Vivier, M., Völk, H. J., Volpe, F., Wagner, S. J., Ward, M., Zdziarski, A. A., and Zech, A.
2008 , Astronomy and Astrophysics, Volume 488, Issue 1, 2008, pp.219-223
Abstract:

Aims. Observations of Kepler's supernova remnant (G4.5+6.8) with the HESS telescope array in 2004 and 2005 with a total live time of 13 h are presented.

Methods. Stereoscopic imaging of Cherenkov radiation from extensive air showers is used to reconstruct the energy and direction of the incident gamma rays.

Results. No evidence for a very high energy (VHE: >100 GeV) gamma-ray signal from the direction of the remnant is found. An upper limit (99% confidence level) on the energy flux in the range 230 GeV{-}12.8 TeV of 8.6 × 10-13 erg cm-2 s-1 is obtained.

Conclusions. In the context of an existing theoretical model for the remnant, the lack of a detectable gamma-ray flux implies a distance of at least 6.4 kpc. A corresponding upper limit for the density of the ambient matter of 0.7 cm-3 is derived. With this distance limit, and assuming a spectral index Γ = 2, the total energy in accelerated protons is limited to Ep < 8.6 × 1049 erg. In the synchrotron/inverse Compton framework, extrapolating the power law measured by RXTE between 10 and 20 keV down in energy, the predicted gamma-ray flux from inverse Compton scattering is below the measured upper limit for magnetic field values greater than 52 μ G.
HESS very-high-energy gamma-ray sources without identified counterparts
Aharonian, F., Akhperjanian, A. G., Barres de Almeida, U., Bazer-Bachi, A. R., Behera, B., Beilicke, M., Benbow, W., Bernlöhr, K., Boisson, C., Bolz, O., Borrel, V., Braun, I., Brion, E., Brown, A. M., Bühler, R., Bulik, T., Büsching, I., Boutelier, T., Carrigan, S., Chadwick, P. M., Chounet, L.-M., Clapson, A. C., Coignet, G., Cornils, R., Costamante, L., Dalton, M., Degrange, B., Dickinson, H. J., Djannati-Ataï, A., Domainko, W., Drury, L. O., Dubois, F., Dubus, G., Dyks, J., Egberts, K., Emmanoulopoulos, D., Espigat, P., Farnier, C., Feinstein, F., Fiasson, A., Förster, A., Fontaine, G., Funk, S., Füßling, M., Gallant, Y. A., Giebels, B., Glicenstein, J. F., Glück, B., Goret, P., Hadjichristidis, C., Hauser, D., Hauser, M., Heinzelmann, G., Henri, G., Hermann, G., Hinton, J. A., Hoffmann, A., Hofmann, W., Holleran, M., Hoppe, S., Horns, D., Jacholkowska, A., de Jager, O. C., Jung, I., Katarzyński, K., Kendziorra, E., Kerschhaggl, M., Khélifi, B., Keogh, D., Komin, N., Kosack, K., Lamanna, G., Latham, I. J., Lemière, A., Lemoine-Goumard, M., Lenain, J.-P., Lohse, T., Martin, J. M., Martineau-Huynh, O., Marcowith, A., Masterson, C., Maurin, D., Maurin, G., McComb, T. J. L., Moderski, R., Moulin, E., de Naurois, M., Nedbal, D., Nolan, S. J., Ohm, S., Olive, J.-P., de Oña Wilhelmi, E., Orford, K. J., Osborne, J. L., Ostrowski, M., Panter, M., Pedaletti, G., Pelletier, G., Petrucci, P.-O., Pita, S., Pühlhofer, G., Punch, M., Ranchon, S., Raubenheimer, B. C., Raue, M., Rayner, S. M., Renaud, M., Ripken, J., Rob, L., Rolland, L., Rosier-Lees, S., Rowell, G., Rudak, B., Ruppel, J., Sahakian, V., Santangelo, A., Schlickeiser, R., Schöck, F., Schröder, R., Schwanke, U., Schwarzburg, S., Schwemmer, S., Shalchi, A., Sol, H., Spangler, D., Stawarz, Ł., Steenkamp, R., Stegmann, C., Superina, G., Tam, P. H., Tavernet, J.-P., Terrier, R., van Eldik, C., Vasileiadis, G., Venter, C., Vialle, J. P., Vincent, P., Vivier, M., Völk, H. J., Volpe, F., Wagner, S. J., Ward, M., Zdziarski, A. A., and Zech, A.
2008 , Astronomy and Astrophysics, Volume 477, Issue 1, January I 2008, pp.353-363
Abstract:

Context. The detection of gamma rays in the very-high-energy (VHE) energy range (100 GeV-100 TeV) provides a direct view of the parent population of ultra-relativistic particles found in astrophysical sources. For this reason, VHE gamma rays are useful for understanding the underlying astrophysical processes in non-thermal sources.

Aims. We investigate unidentified VHE gamma-ray sources that have been discovered with HESS in the most sensitive blind survey of the Galactic plane at VHE energies conducted so far.

Methods. The HESS array of imaging atmospheric Cherenkov telescopes (IACTs) has a high sensitivity compared with previous instruments (~0.01 Crab in 25 h observation time for a 5σ point-source detection), and with its large field of view, is well suited for scan-based observations. The on-going HESS survey of the inner Galaxy has revealed a large number of new VHE sources, and for each we attempt to associate the VHE emission with multi-wavelength data in the radio through X-ray wavebands.

Results. For each of the eight unidentified VHE sources considered here, we present the energy spectra and sky maps of the sources and their environment. The VHE morphology is compared with available multi-wavelength data (mainly radio and X-rays). No plausible counterparts are found.
High energy polarization of pulsars-observations vs. models
Słowikowska, A., Rudak, B., and Kanbach, G.
2008 , 40 YEARS OF PULSARS: Millisecond Pulsars, Magnetars and More. AIP Conference Proceedings, Volume 983, pp. 142-144 (2008).
Abstract:
We review selected polarimetric observations of five pulsars in the optical energy range. Additionally, the UV/X-ray range observations are included for the Crab pulsar and its nebula. We compare the available theoretical results obtained in the framework of different models with the observed polarization characteristics of pulsar emission. In particular, we present new, high precision optical measurements of the Crab pulsar with time resolution of 10 μs. The high photon statistics allows us to identify the fine features in the phase dependencies of polarization degree (P.D.) and position angle (P.A.) of linear polarization never resolved before. The phase-resolved optical polarization characteristics show surprising correlations with the phase structure at radio frequencies. This subtle connection between presumed coherent and non-coherent emission, which have also been detected between the giant radio pulses and the optical intensity of the Crab pulsar [1], calls for more elaborate theoretical models than those currently available.
HST Snapshot Survey of Post-AGB Objects
Siódmiak, N., Meixner, M., Ueta, T., Sugerman, B. E. K., Van de Steene, G. C., and Szczerba, R.
2008 , eprint arXiv:0801.4612
Abstract:
The results from a Hubble Space Telescope (HST) snapshot survey of post-AGB objects are shown. The aim of the survey is to complement existing HST images of PPN and to connect various types of nebulosities with physical and chemical properties of their central stars. Nebulosities are detected in 15 of 33 sources. Images and photometric and geometric measurements are presented. For sources with nebulosities we see a morphological bifurcation into two groups, DUPLEX and SOLE, as previous studies have found. We find further support to the previous results suggesting that this dichotomy is caused by a difference in optical thickness of the dust shell. The remaining 18 sources are classified as stellar post-AGB objects, because our observations indicate a lack of nebulosity. We show that some stellar sources may in fact be DUPLEX or SOLE based on their infrared colors. The cause of the differences among the groups are investigated. We discuss some evidence suggesting that high progenitor-mass AGB stars tend to become DUPLEX post-AGB objects. Intermediate progenitor-mass AGB stars tend to be SOLE post-AGB objects. Most of the stellar sources probably have low mass progenitors and do not seem to develop nebulosities during the post-AGB phase and therefore do not become planetary nebulae.
Hubble Space Telescope Snapshot Survey of Post-AGB Objects
Siódmiak, N., Meixner, M., Ueta, T., Sugerman, B. E. K., Van de Steene, G. C., and Szczerba, R.
2008 , The Astrophysical Journal, Volume 677, Issue 1, pp. 382-400.
Abstract:
The results of a Hubble Space Telescope (HST) snapshot survey of post-AGB objects are shown. The aim of the survey is to complement existing HST images of protoplanetary nebulae and to connect various types of nebulosities with the physical and chemical properties of their central stars. Nebulosities are detected in 15 of 33 sources. Images and photometric and geometric measurements are presented. For sources with nebulosities we see a morphological bifurcation into two groups, DUPLEX and SOLE, as previous studies have found. We find further support for the previous results, suggesting that this dichotomy is caused by a difference in the optical thickness of the dust shell. The remaining 18 sources are classified as stellar post-AGB objects, because our observations indicate a lack of nebulosity. We show that some stellar sources may in fact be DUPLEX or SOLE objects based on their infrared colors. The causes of the differences among the groups are investigated. We discuss some evidence suggesting that high progenitor mass AGB stars tend to become DUPLEX post-AGB objects and intermediate progenitor mass AGB stars tend to become SOLE post-AGB objects. Most of the stellar sources probably have low-mass progenitors and do not seem to develop nebulosities during the post-AGB phase; therefore, they do not become planetary nebulae.
Limits on an Energy Dependence of the Speed of Light from a Flare of the Active Galaxy PKS 2155-304
Aharonian, F., Akhperjanian, A. G., Barres de Almeida, U., Bazer-Bachi, A. R., Becherini, Y., Behera, B., Beilicke, M., Benbow, W., Bernlöhr, K., Boisson, C., Bochow, A., Borrel, V., Braun, I., Brion, E., Brucker, J., Brun, P., Bühler, R., Bulik, T., Büsching, I., Boutelier, T., Carrigan, S., Chadwick, P. M., Charbonnier, A., Chaves, R. C. G., Chounet, L.-M., Clapson, A. C., Coignet, G., Costamante, L., Dalton, M., Degrange, B., Deil, C., Dickinson, H. J., Djannati-Ataï, A., Domainko, W., Drury, L. O. '., Dubois, F., Dubus, G., Dyks, J., Egberts, K., Emmanoulopoulos, D., Espigat, P., Farnier, C., Feinstein, F., Fiasson, A., Förster, A., Fontaine, G., Füßling, M., Gabici, S., Gallant, Y. A., Gérard, L., Giebels, B., Glicenstein, J. F., Glück, B., Goret, P., Hadjichristidis, C., Hauser, D., Hauser, M., Heinz, S., Heinzelmann, G., Henri, G., Hermann, G., Hinton, J. A., Hoffmann, A., Hofmann, W., Holleran, M., Hoppe, S., Horns, D., Jacholkowska, A., de Jager, O. C., Jung, I., Katarzyński, K., Kaufmann, S., Kendziorra, E., Kerschhaggl, M., Khangulyan, D., Khélifi, B., Keogh, D., Komin, N., Kosack, K., Lamanna, G., Lenain, J.-P., Lohse, T., Marandon, V., Martin, J. M., Martineau-Huynh, O., Marcowith, A., Maurin, D., McComb, T. J. L., Medina, C., Moderski, R., Moulin, E., Naumann-Godo, M., de Naurois, M., Nedbal, D., Nekrassov, D., Niemiec, J., Nolan, S. J., Ohm, S., Olive, J.-F., de Oña Wilhelmi, E., Orford, K. J., Osborne, J. L., Ostrowski, M., Panter, M., Pedaletti, G., Pelletier, G., Petrucci, P.-O., Pita, S., Pühlhofer, G., Punch, M., Quirrenbach, A., Raubenheimer, B. C., Raue, M., Rayner, S. M., Renaud, M., Rieger, F., Ripken, J., Rob, L., Rosier-Lees, S., Rowell, G., Rudak, B., Ruppel, J., Sahakian, V., Santangelo, A., Schlickeiser, R., Schöck, F. M., Schröder, R., Schwanke, U., Schwarzburg, S., Schwemmer, S., Shalchi, A., Skilton, J. L., Sol, H., Spangler, D., Stawarz, Ł., Steenkamp, R., Stegmann, C., Superina, G., Tam, P. H., Tavernet, J.-P., Terrier, R., Tibolla, O., van Eldik, C., Vasileiadis, G., Venter, C., Vialle, J. P., Vincent, P., Vivier, M., Völk, H. J., Volpe, F., Wagner, S. J., Ward, M., Zdziarski, A. A., and Zech, A.
2008 , Physical Review Letters, vol. 101, Issue 17, id. 170402
Abstract:
In the past few decades, several models have predicted an energy dependence of the speed of light in the context of quantum gravity. For cosmological sources such as active galaxies, this minuscule effect can add up to measurable photon-energy dependent time lags. In this Letter a search for such time lags during the High Energy Stereoscopic System observations of the exceptional very high energy flare of the active galaxy PKS 2155-304 on 28 July 2006 is presented. Since no significant time lag is found, lower limits on the energy scale of speed of light modifications are derived.
Masses, Luminosities, and Orbital Coplanarities of the μ Orionis Quadruple-Star System from Phases Differential Astrometry
Muterspaugh, M. W., Lane, B. F., Fekel, F. C., Konacki, M., Burke, B. F., Kulkarni, S. R., Colavita, M. M., Shao, M., and Wiktorowicz, S. J.
2008 , The Astronomical Journal, Volume 135, Issue 3, pp. 766-776 (2008).
Abstract:
μ Orionis was identified by spectroscopic studies as a quadruple-star system. Seventeen high-precision differential astrometry measurements of
μ Ori have been collected by the Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES). These show both the motion of the long-period binary orbit and short-period perturbations superimposed on that caused by each of the components in the long-period system being themselves binaries. The new measurements enable the orientations of the long-period binary and short-period subsystems to be determined. Recent theoretical work predicts the distribution of relative inclinations between inner and outer orbits of hierarchical systems to peak near 40 and 140 degrees. The degree of coplanarity of this complex system is determined, and the angle between the planes of the A-B and Aa-Ab orbits is found to be 136.7 ± 8.3 degrees, near the predicted distribution peak at 140 degrees; this result is discussed in the context of the handful of systems with established mutual inclinations. The system distance and masses for each component are obtained from a combined fit of the PHASES astrometry and archival radial velocity observations. The component masses have relative precisions of 5% (component Aa), 15% (Ab), and 1.4% (each of Ba and Bb). The median size of the minor axes of the uncertainty ellipses for the new measurements is 20 micro-arcseconds (μas). Updated orbits for δ Equulei, κ Pegasi, and V819 Herculis are also presented.
PAH anions as carriers of the mid-IR emission bands in planetary nebulae
Szczerba, R., Joblin, C., Berné, O., and Szyszka, C.
2008 , Organic Matter in Space, Proceedings of the International Astronomical Union, IAU Symposium, Volume 251, p. 207-212
Abstract:
We present results of the mid-IR spectra decomposition for planetary nebulae and compact H ii regions in our Galaxy and Magellanic Clouds. The striking correlation between the required PAH component with “7.7” μm band shifted to about 7.8 μm and electron densities of the modeled sources allows us to argue that this PAH component may be in fact PAH anions (PAH).
Precise Astrometry of Visual Binaries with Adaptive Optics. A Way for Finding Exoplanets?
Hełminiak, K. and Konacki, M.
2008 , eprint arXiv:0807.4139
Abstract:
We present the results of our study of astrometric stability of 200-in Hale (Mt. Palomar) and 10-m Keck II (Mauna Kea) telescopes, both with Adaptive Optics (AO) facilities. A group of nearby visual binaries and multiples was observed in near infrared, relative separations and position angles measured. We have also checked the influence of some systematic effects (e.g. atmospherical refraction, varying plate scale factor) on result and precision of astrometric measurements. We conclude that in visual binaries astrometrical observations it is possible to achieve much better precision than 1 miliarcsecond, which in many cases allows detection of the astrometrical signal produced by planetary-mass object.
Properties of [WC] Planetary Nebulae
Górny, S. K.
2008 , Hydrogen-Deficient Stars ASP Conference Series, Vol. 391, proceedings of the conference held 17-21 September, 2007, at Eberhard Karls University, T&uuml;bingen, Germany. Edited by Klaus Werner and Thomas Rauch. San Francisco: Astronomical Society of the Pacific, 2008., p.165
Abstract:
The origin of the hydrogen deficient [WC] type central stars of planetary nebulae remains an open question in the theory of intermediate mass stars. In this review we present the results of the analysis concerning the nebulae surrounding these unusual nuclei. The properties of these nebulae bring important information on the evolutionary status of [WC] objects and constrain the possible theoretical scenarios.
Search for gamma rays from dark matter annihilations around intermediate mass black holes with the HESS experiment
Aharonian, F., Akhperjanian, A. G., de Almeida, U. B., Bazer-Bachi, A. R., Behera, B., Beilicke, M., Benbow, W., Bernlöhr, K., Bertone, G., Boisson, C., Bochow, A., Borrel, V., Braun, I., Brion, E., Brucker, J., Brun, P., Bühler, R., Bulik, T., Büsching, I., Boutelier, T., Carrigan, S., Chadwick, P. M., Chaves, R. C. G., Chounet, L.-M., Clapson, A. C., Coignet, G., Costamante, L., Dalton, M., Degrange, B., Dickinson, H. J., Djannati-Ataï, A., Domainko, W., Drury, L. O. '., Dubois, F., Dubus, G., Dyks, J., Egberts, K., Emmanoulopoulos, D., Espigat, P., Farnier, C., Feinstein, F., Fiasson, A., Förster, A., Fontaine, G., Füßling, M., Gabici, S., Gallant, Y. A., Gérard, L., Giebels, B., Glicenstein, J. F., Glück, B., Goret, P., Hadjichristidis, C., Hauser, D., Hauser, M., Heinzelmann, G., Henri, G., Hermann, G., Hinton, J. A., Hoffmann, A., Hofmann, W., Holleran, M., Hoppe, S., Horns, D., Jacholkowska, A., de Jager, O. C., Jung, I., Katarzyński, K., Kaufmann, S., Kendziorra, E., Kerschhaggl, M., Khangulyan, D., Khélifi, B., Keogh, D., Komin, N., Kosack, K., Lamanna, G., Latham, I. J., Lenain, J.-P., Lohse, T., Marandon, V., Martin, J. M., Martineau-Huynh, O., Marcowith, A., Masterson, C., Maurin, D., McComb, T. J. L., Moderski, R., Moulin, E., Naumann-Godo, M., de Naurois, M., Nedbal, D., Nekrassov, D., Niemiec, J., Nolan, S. J., Ohm, S., Olive, J.-P., de Oñawilhelmi, E., Orford, K. J., Osborne, J. L., Ostrowski, M., Panter, M., Pedaletti, G., Pelletier, G., Petrucci, P.-O., Pita, S., Pühlhofer, G., Punch, M., Quirrenbach, A., Raubenheimer, B. C., Raue, M., Rayner, S. M., Renaud, M., Rieger, F., Ripken, J., Rob, L., Rosier-Lees, S., Rowell, G., Rudak, B., Ruppel, J., Sahakian, V., Santangelo, A., Schlickeiser, R., Schöck, F. M., Schröder, R., Schwanke, U., Schwarzburg, S., Schwemmer, S., Shalchi, A., Skilton, J. L., Sol, H., Spangler, D., Stawarz, Ł., Steenkamp, R., Stegmann, C., Superina, G., Tam, P. H., Tavernet, J.-P., Terrier, R., Tibolla, O., van Eldik, C., Vasileiadis, G., Venter, C., Vialle, J. P., Vincent, P., Vivier, M., Völk, H. J., Volpe, F., Wagner, S. J., Ward, M., Zdziarski, A. A., and Zech, A.
2008 , Physical Review D, vol. 78, Issue 7, id. 072008
Abstract:
The HESS array of Cherenkov telescopes has performed, from 2004 to 2007, a survey of the inner galactic plane at photon energies above 100 GeV. About 400 hours of data have been accumulated in the region between -30 and +60degrees in galactic longitude, and between -3 and +3degrees in galactic latitude. Assuming that dark matter is composed of weakly interacting massive particles, we calculate here the HESS sensitivity map for dark matter annihilations, and derive the first experimental constraints on the (”minispikes”) scenario, in which a gamma-ray signal arises from dark matter annihilation around intermediate mass black holes. The data exclude the proposed scenario at a 90% confidence level for dark matter particles with velocity-weighted annihilation cross section σv above 10-28cm3s-1 and mass between 800 GeV and 10 TeV.
Simultaneous HESS and Chandra observations of Sagitarius Astar during an X-ray flare
Aharonian, F., Akhperjanian, A. G., Barres de Almeida, U., Bazer-Bachi, A. R., Becherini, Y., Behera, B., Benbow, W., Bernlöhr, K., Boisson, C., Bochow, A., Borrel, V., Braun, I., Brion, E., Brucker, J., Brun, P., Bühler, R., Bulik, T., Büsching, I., Boutelier, T., Carrigan, S., Chadwick, P. M., Charbonnier, A., Chaves, R. C. G., Cheesebrough, A., Chounet, L.-M., Clapson, A. C., Coignet, G., Dalton, M., Degrange, B., Deil, C., Dickinson, H. J., Djannati-Ataï, A., Domainko, W., O'C. Drury, L., Dubois, F., Dubus, G., Dyks, J., Dyrda, M., Egberts, K., Emmanoulopoulos, D., Espigat, P., Farnier, C., Feinstein, F., Fiasson, A., Förster, A., Fontaine, G., Füßling, M., Gabici, S., Gallant, Y. A., Gérard, L., Giebels, B., Glicenstein, J. F., Glück, B., Goret, P., Hadjichristidis, C., Hauser, D., Hauser, M., Heinz, S., Heinzelmann, G., Henri, G., Hermann, G., Hinton, J. A., Hoffmann, A., Hofmann, W., Holleran, M., Hoppe, S., Horns, D., Jacholkowska, A., de Jager, O. C., Jung, I., Katarzyński, K., Kaufmann, S., Kendziorra, E., Kerschhaggl, M., Khangulyan, D., Khélifi, B., Keogh, D., Komin, N., Kosack, K., Lamanna, G., Lenain, J.-P., Lohse, T., Marandon, V., Martin, J. M., Martineau-Huynh, O., Marcowith, A., Maurin, D., McComb, T. J. L., Medina, M. C., Moderski, R., Moulin, E., Naumann-Godo, M., de Naurois, M., Nedbal, D., Nekrassov, D., Niemiec, J., Nolan, S. J., Ohm, S., Olive, J.-F., de Oña Wilhelmi, E., Orford, K. J., Osborne, J. L., Ostrowski, M., Panter, M., Pedaletti, G., Pelletier, G., Petrucci, P.-O., Pita, S., Pühlhofer, G., Punch, M., Quirrenbach, A., Raubenheimer, B. C., Raue, M., Rayner, S. M., Renaud, M., Rieger, F., Ripken, J., Rob, L., Rosier-Lees, S., Rowell, G., Rudak, B., Rulten, C. B., Ruppel, J., Sahakian, V., Santangelo, A., Schlickeiser, R., Schöck, F. M., Schröder, R., Schwanke, U., Schwarzburg, S., Schwemmer, S., Shalchi, A., Skilton, J. L., Sol, H., Spangler, D., Stawarz, Ł., Steenkamp, R., Stegmann, C., Superina, G., Tam, P. H., Tavernet, J.-P., Terrier, R., Tibolla, O., van Eldik, C., Vasileiadis, G., Venter, C., Vialle, J. P., Vincent, P., Vivier, M., Völk, H. J., Volpe, F., Wagner, S. J., Ward, M., Zdziarski, A. A., and Zech, A.
2008 , Astronomy and Astrophysics, Volume 492, Issue 1, 2008, pp.L25-L28
Abstract:
The rapidly varying ( 10 min timescale) non-thermal X-ray emission observed from Sgr Astar implies that particle acceleration is occuring close to the event horizon of the supermassive black hole. The TeV γ-ray source HESS J1745-290 is coincident with Sgr Astar and may be closely related to its X-ray emission. Simultaneous X-ray and TeV observations are required to elucidate the relationship between these objects. We report on joint HESS/Chandra observations performed in July 2005, during which an X-ray flare was detected. Despite a factor of ≈9 increase in the X-ray flux of Sgr Astar, no evidence is found for an increase in the TeV γ-ray flux from this region. We find that an increase in the γ-ray flux of a factor of 2 or greater can be excluded at a confidence level of 99%. This finding disfavours scenarios in which the keV and TeV emission are associated with the same population of accelerated particles and in which the bulk of the γ-ray emission is produced within 1014 cm ( 100 R_S) of the supermassive black hole.
The Herschel-Heterodyne Instrument for the Far-Infrared (HIFI): instrument and pre-launch testing
de Graauw, T., Whyborn, N., Helmich, F., Dieleman, P., Roelfsema, P., Caux, E., Phillips, T., Stutzki, J., Beintema, D., Benz, A., Biver, N., Boogert, A., Boulanger, F., Cherednichenko, S., Coeur-Joly, O., Comito, C., Dartois, E., de Jonge, A., de Lange, G., Delorme, I., DiGiorgio, A., Dubbeldam, L., Edwards, K., Fich, M., Güsten, R., Herpin, F., Honingh, N., Huisman, R., Jacobs, H., Jellema, W., Kawamura, J., Kester, D., Klapwijk, T., Klein, T., Kooi, J., Krieg, J.-M., Kramer, C., Kruizenga, B., Laauwen, W., Larsson, B., Leinz, C., Liseau, R., Lord, S., Luinge, W., Marston, A., Merkel, H., Moreno, R., Morris, P., Murphy, A., Naber, A., Planesas, P., Martin-Pintado, J., Olberg, M., Orleanski, P., Ossenkopf, V., Pearson, J., Perault, M., Phillip, S., Rataj, M., Ravera, L., Saraceno, P., Schieder, R., Schmuelling, F., Szczerba, R., Shipman, R., Teyssier, D., Vastel, C., Visser, H., Wildeman, K., Wafelbakker, K., Ward, J., Higgins, R., Aarts, H., Tielens, X., and Zaal, P.
2008 , Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter. Edited by Oschmann, Jacobus M., Jr.; de Graauw, Mattheus W. M.; MacEwen, Howard A. Proceedings of the SPIE, Volume 7010, pp. 701004-701004-14 (2008).
Abstract:
This paper describes the Heterodyne Instrument for the Far-Infrared (HIFI), to be launched onboard of ESA's Herschel Space Observatory, by 2008. It includes the first results from the instrument level tests. The instrument is designed to be electronically tuneable over a wide and continuous frequency range in the Far Infrared, with velocity resolutions better than 0.1 km/s with a high sensitivity. This will enable detailed investigations of a wide variety of astronomical sources, ranging from solar system objects, star formation regions to nuclei of galaxies. The instrument comprises 5 frequency bands covering 480-1150 GHz with SIS mixers and a sixth dual frequency band, for the 1410-1910 GHz range, with Hot Electron Bolometer Mixers (HEB). The Local Oscillator (LO) subsystem consists of a dedicated Ka-band synthesizer followed by 7 times 2 chains of frequency multipliers, 2 chains for each frequency band. A pair of Auto-Correlators and a pair of Acousto-Optic spectrometers process the two IF signals from the dual-polarization front-ends to provide instantaneous frequency coverage of 4 GHz, with a set of resolutions (140 kHz to 1 MHz), better than < 0.1 km/s. After a successful qualification program, the flight instrument was delivered and entered the testing phase at satellite level. We will also report on the pre-flight test and calibration results together with the expected in-flight performance.
Upper limits from HESS active galactic nuclei observations in 2005-2007
Aharonian, F., Akhperjanian, A. G., Barres de Almeida, U., Bazer-Bachi, A. R., Behera, B., Beilicke, M., Benbow, W., Bernlöhr, K., Boisson, C., Bolz, O., Borrel, V., Braun, I., Brion, E., Brown, A. M., Bühler, R., Bulik, T., Büsching, I., Boutelier, T., Carrigan, S., Chadwick, P. M., Chounet, L.-M., Clapson, A. C., Coignet, G., Cornils, R., Costamante, L., Dalton, M., Degrange, B., Dickinson, H. J., Djannati-Ataï, A., Domainko, W., O'C. Drury, L., Dubois, F., Dubus, G., Dyks, J., Egberts, K., Emmanoulopoulos, D., Espigat, P., Farnier, C., Feinstein, F., Fiasson, A., Förster, A., Fontaine, G., Funk, S., Füßling, M., Gallant, Y. A., Giebels, B., Glicenstein, J. F., Glück, B., Goret, P., Hadjichristidis, C., Hauser, D., Hauser, M., Heinzelmann, G., Henri, G., Hermann, G., Hinton, J. A., Hoffmann, A., Hofmann, W., Holleran, M., Hoppe, S., Horns, D., Jacholkowska, A., de Jager, O. C., Jung, I., Katarzyński, K., Kendziorra, E., Kerschhaggl, M., Khélifi, B., Keogh, D., Komin, N., Kosack, K., Lamanna, G., Latham, I. J., Lemière, A., Lemoine-Goumard, M., Lenain, J.-P., Lohse, T., Martin, J. M., Martineau-Huynh, O., Marcowith, A., Masterson, C., Maurin, D., Maurin, G., McComb, T. J. L., Moderski, R., Moulin, E., de Naurois, M., Nedbal, D., Nolan, S. J., Ohm, S., Olive, J.-P., de Oña Wilhelmi, E., Orford, K. J., Osborne, J. L., Ostrowski, M., Panter, M., Pedaletti, G., Pelletier, G., Petrucci, P.-O., Pita, S., Pühlhofer, G., Punch, M., Ranchon, S., Raubenheimer, B. C., Raue, M., Rayner, S. M., Renaud, M., Ripken, J., Rob, L., Rolland, L., Rosier-Lees, S., Rowell, G., Rudak, B., Ruppel, J., Sahakian, V., Santangelo, A., Schlickeiser, R., Schöck, F., Schröder, R., Schwanke, U., Schwarzburg, S., Schwemmer, S., Shalchi, A., Sol, H., Spangler, D., Stawarz, Ł., Steenkamp, R., Stegmann, C., Superina, G., Tam, P. H., Tavernet, J.-P., Terrier, R., van Eldik, C., Vasileiadis, G., Venter, C., Vialle, J. P., Vincent, P., Vivier, M., Völk, H. J., Volpe, F., Wagner, S. J., Ward, M., Zdziarski, A. A., and Zech, A.
2008 , Astronomy and Astrophysics, Volume 478, Issue 2, February I 2008, pp.387-393
Abstract:
Aims:Very high energy (VHE; E>100 GeV) γ-ray studies were performed for 18 active galactic nuclei (AGN) from a variety of AGN classes.

Methods. VHE observations of a sample of 14 AGN, considered candidate VHE emitters, were made with the High Energy Stereoscopic System (HESS) between January 2005 and July 2007. Large-zenith-angle observations of three northern AGN (Mkn 421, Mkn 501, 1ES 1218+304), known to emit VHE γ-rays, were also performed in order to sample their spectral energy distributions (SEDs) above 1 TeV. In addition, the VHE flux from 1ES 1101-232, previously detected by HESS in 2004-2005, was monitored during 2006 and 2007.

Results. As significant detections from the HESS observation program are reported elsewhere, the results reported here are primarily integral flux upper limits. The average exposure for each of the 14 VHE-candidate AGN is ~7 h live time, and the observations have an average energy threshold between 230 GeV and 590 GeV. Upper limits for these 14 AGN range from <0.9% to <4.9% of the Crab Nebula flux, and eight of these are the most constraining ever reported for the object. The brief (<2.2 h each) large-zenith-angle observations yield upper limits for Mkn 501 (<20% Crab above 2.5 TeV) and 1ES 1218+304 (<17% Crab above 1.0 TeV), and a marginal detection (3.5σ) of Mkn 421 (50% Crab above 2.1 TeV). 1ES 1101-232 was marginally detected (3.6σ, 1.7% Crab above 260 GeV) during the 2006 (13.7 h live time) observations, but not in the 2007 (4.6 h live time) data. The upper limit in 2007 (<1.9% Crab above 260 GeV) is below the average flux measured by HESS from 2004-2006.
© Centrum Astronomiczne im. M. Kopernika PAN w Toruniu